The subject matter disclosed herein relates to power plant systems and, more particularly, to systems for emissions sensitive transient state operation of a combined-cycle power plant system.
The operation of some power plant systems, for example certain simple-cycle and combined-cycle power plant systems, produce emissions (i.e. Carbon Monoxide (CO), hydrocarbons (UHC), Nitrogen Oxide (NOx) etc.) which must be released/dissipated into the atmosphere. The release of these emissions may damage the environment and/or be regulated by certain agencies. A significant quantity of these emissions may be generated during states of transient operation (e.g. start-up, shutdown, etc.), where operational steam temperatures are restricted and components of the power plant system may operate with decreased loads.
In combined-cycle power plant systems, a temperature of the steam supplied to the steam turbine during startup or other transient operation may be controlled by adjusting an operating parameter of the system (e.g., the gas turbine load, gas turbine exhaust temperature, etc.). During startup or other transient operation, the allowable operational steam temperature which may be supplied to the steam turbine is restricted to a temperature range which may be limited by the temperature of the steam turbine components. The steam temperatures within this allowable range are held close to the temperature of the system components so as to prevent against component binding and the formation of thermal stresses. In determining this temperature range and the appropriate operational steam temperature, current power plant systems consider a number of factors (e.g. effect on start-up and/or cool-down time, material effects on components, etc.). However, these systems are blind to emissions variances which may exist within the allowable steam temperature range. As such, emissions effects are not considered when adjusting operating parameters, such as the gas turbine load, to attain an operational steam temperature for transient state operation.